Popular smoking articles, such as cigarettes, have a substantially cylindrical rod-shaped structure and include a charge, roll or column of smokable material, such as shredded tobacco (e.g., in cut filler form), surrounded by a paper wrapper, thereby forming a so-called “smokable rod” or “tobacco rod.” Normally, a cigarette has a cylindrical filter element aligned in an end-to-end relationship with the tobacco rod. Typically, a filter element comprises plasticized cellulose acetate tow circumscribed by a paper material known as “plug wrap.” Typically, the filter element is attached to one end of the tobacco rod using a circumscribing wrapping material known as “tipping paper.” It also has become desirable to perforate the tipping material and plug wrap, in order to provide dilution of drawn mainstream smoke with ambient air. Descriptions of cigarettes and the various components thereof are set forth in Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999). A cigarette is employed by a smoker by lighting one end thereof and burning the tobacco rod. The smoker then receives mainstream smoke into his/her mouth by drawing on the opposite end (e.g., the filter end) of the cigarette.
Certain filter elements for cigarettes contain materials that alter the chemical composition or sensory characteristics of mainstream smoke. For example, it is known to incorporate certain adsorbent materials into a filter element, such as activated carbon or charcoal materials (collectively, carbonaceous materials) in particulate or granular form. Granules of carbonaceous material can be incorporated into “dalmatian” types of filter regions using the general types of techniques used for traditional dalmatian filter manufacture. Techniques for production of dalmatian filters are known, and representative dalmatian filters have been provided commercially by Filtrona Greensboro Inc. Alternatively, granules of carbonaceous material can be incorporated into “cavity” types of filter regions using the general types of techniques used for traditional “cavity” filter manufacture. Various types of filters incorporating charcoal particles or activated carbon types of materials are set forth in U.S. Pat. No. 2,881,770 to Touey; U.S. Pat. No. 3,101,723 to Seligman et al.; U.S. Pat. No. 3,236,244 to Irby et al.; U.S. Pat. No. 3,311,519 to Touey et al.; U.S. Pat. No. 3,313,306 to Berger; U.S. Pat. No. 3,319,629 to Chamberlain; U.S. Pat. No. 3,347,247 to Lloyd; U.S. Pat. No. 3,349,780 to Sublett et al.; U.S. Pat. No. 3,370,595 to Davis et al.; 3,413,982 to Sublett et al.; U.S. Pat. No. 3,551,256 to Watson; U.S. Pat. No. 3,602,231 to Dock; U.S. Pat. No. 3,904,577 to Buisson; U.S. Pat. No. 3,972,335 to Tigglebeck et al.; U.S. Pat. No. 5,360,023 to Blakley et al.; U.S. Pat. No. 5,909,736 to Stpyridis; and U.S. Pat. No. 6,537,186 to Veluz; US Pat. Publication Nos. 2003/0034085 to Spiers et al.; 2003/0106562 to Chatterjee; 2005/0066982 to Clark et al; 2006/0025292 to Hicks et al.; 2007/0056600 to Coleman, III et al.; 2008/0142028 to Fagg; 2008/0173320 to Dunlap et al.; 2008/0295853 to Jones; 2009/0288672 to Hutchens; PCT WO 2006/064371 to Banerjea et al.; PCT WO 2006/051422 to Jupe et al.; and PCT WO2006/103404 to Cashmore et al., which are incorporated herein by reference.
Various methods and apparatuses have been developed to manufacture filter elements containing fibrous tow material combined with an adsorbent material or other particulate additive. For example, techniques for production of dalmatian filters are known, and representative dalmatian filters have been provided commercially by Filtrona Greensboro Inc. Carbon particles can be incorporated into cavity types of filter regions using the general types of techniques used for traditional cavity filter manufacture. See, for example, the types of equipment and techniques that can be used for, or suitably modified for use for, incorporating materials into filters that are set forth in U.S. Pat. No. 3,844,200 to Sexstone; U.S. Pat. No. 4,016,830 to Sexstone; U.S. Pat. No. 4,214,508 to Washington; U.S. Pat. No. 4,425,107 to Hall; U.S. Pat. No. 4,411,640 to Hall; U.S. Pat. No. 5,322,495 to Budjinski II et al; U.S. Pat. No. 5,656,412 to Ercelebi et al and U.S. Pat. No. 6,837,281 to Spiers et al.; which are incorporated herein by reference. Other arrangements for inserting objects into filter material are disclosed, for example, in U.S. Pat. No. 4,281,671 to Byrne et al. and U.S. Pat. No. 7,115,085 to Deal; US Pat. Appl. Pub. Nos. 2007/0068540 to Thomas et al.; 2008/0029118 to Nelson et al.; 2008/0142028 to Fagg; 2008/0302373 to Stokes et al; 2009/0288667 to Andresen et al.; 2009/0288672 to Hutchens and 2010/0101589 to Nelson et al.; and U.S. patent application Ser. No. 12/407,260, filed Mar. 19, 2009, which are incorporated herein by reference.
The currently available filter technology for incorporation of a particulate additive into a filter element suffers from several drawbacks. Cavity filters that include a particulate additive in a free state, such as activated carbon particles, could potentially result in contamination of mainstream smoke and can also suffer from channeling of smoke around the loose bed of particles in the cavity. In addition, manufacturing methods for incorporating particulate additives in cavity filters can be challenging due to particulate dust clouds created during the process. Affixing a particulate adsorbent within a fibrous tow typically involves use of a plasticizer or other adhesive material to adhere the particles within the fibrous mass, which can lead to deactivation of the adsorbent due to contamination of the surface of the particles by the plasticizer or adhesive.
There remains a need in the art for multifunctional filter elements that provide multiple different mechanisms for filtration of mainstream smoke, and which can be manufactured in a simple manner with minimal modification of existing filter manufacturing equipment and processes.